Counter-terror police have been drafted in to help with a major hate crime investigation after a small home-made bomb exploded near a mosque.
Around 150 people were evacuated from their homes in the Caldmore area of Walsall on Saturday night while bomb disposal experts made the device safe.
West Midlands Police said a loud bang heard by residents late on Friday "appeared to be consistent" with the device exploding. No one was injured and it caused minimal damage.
The remains of the device were found in an alleyway adjoining the Aisha Mosque and Islamic Centre in Rutter Street on Saturday by a local man who took them home and showed them to his wife. The mosque's imam also took them home later before anyone realised their significance.
Assistant Chief Constable Sharon Rowe said: "The force is taking this attack against the mosque very seriously and we have a major investigation under way. To that end, I have called in support from all over the force, including the West Midlands Counter Terrorism Unit, which has a number of experts supporting the inquiry. Specialist investigators have been working all day and continue to ensure that we maximise every opportunity from the crime scene."
She added: "At this stage we are keeping an open mind on a motive, but have recorded it as a hate crime. A hate crime is any criminal act committed against a person or property that is motivated by the offender's hatred of people because of their gender, race, religion, disability or sexual orientation."
Police have stepped up patrols in Walsall to reassure the community, despite believing the planting of the device was an isolated incident.
Bomb disposal experts from the Royal Logistic Corps attended the scene to ensure the device was safe and forensic teams spent several hours conducting a detailed search for evidence. About 80 people evacuated from the area as a precautionary measure overnight were given shelter by Walsall Council, while 70 residents stayed with friends or family.
It comes after a number of recent incidents at mosques following the murder of Drummer Lee Rigby in Woolwich, London.
Last week two men were charged in relation to an alleged arson at a mosque in Gloucester, and an Islamic cultural centre in Grimsby was hit by petrol bombs last month. Mosques in Braintree, Essex, and Gillingham, Kent, have also been targeted.